RF breakdown in low pressure gases in small (millimetric) gaps with non-planar surfaces

Small gaps are present in plasma-enhanced chemical vapor deposition reactors to isolate the RF electrode from the grounded parts of the reactor. These gaps are supposed to be small enough so that no glow discharge can form (dark space shielding), but wide enough to avoid problems of mechanical tolerance and thermal expansion, as well as to limit large capacitive currents and prevent metal vapor arcing due to field emission. RF breakdown in these small gaps is of high interest for the thin-film industry, since arcing and parasitic plasmas in small gaps in PECVD reactors represent a failure point preventing the upscaling to larger substrates and/or higher power regimes for micro-crystalline silicon deposition.